trigger-happy
From Longman Dictionary of Contemporary Englishtrigger-happytrigger-ˌhappy (also trigger-ready) adjective informal DANGEROUSsomeone who is trigger-happy is much too willing to use weapons, especially guns a trigger-happy copExamples from the Corpustrigger-happy• A debate even begins about whether the army is not getting a little trigger-happy in its nervous and no doubt terrified tension.• After all, half-an-hour away in any direction there is a trigger-happy racist waiting for his big day.• trigger-happy soldiers